I have notice this also when I engage pinpoint sizing a foot away this happens but if you engage it right over the target it narrows the signal down and easier to locate must be tuning to that spot .
But when I got off the target pinpointing at that exact spot the detector would blare where ever I would go so it had to be reset seems to be tuning to that spot . sube
But when I got off the target pinpointing at that exact spot the detector would blare where ever I would go so it had to be reset seems to be tuning to that spot . sube